A long battery life is important for current portable communication apparatuses. Thus, research is conducted for increasing a battery capacity and for low power consumption in order to extend the battery life of the portable communication apparatuses.
An embedded system used in the portable communication apparatus is usually a software-based system. Current consumptions of a Central Processing Unit (CPU), which executes the software, and a memory are relatively important in the portable communication apparatus.
Therefore, the portable communication apparatus dynamically controls current during an operation of the CPU in order to reduce current consumption of the embedded system, i.e., when the CPU is in standby mode, the portable communication apparatus reduces the current consumption by lowering a clock of the CPU.
Meanwhile, when the CPU is in the operation mode, the portable communication apparatus provides a current to the CPU in order to supply the clock normally. The portable communication apparatus may minimize the current in the embedded system by using dynamic clock scaling and dynamic voltage scaling.
That is, the portable communication apparatus supplies a high clock or a high voltage when the portable communication apparatus operates fast and the portable communication apparatus supplies a low clock or a low voltage when the portable communication apparatus operates slowly. By doing this procedure, the portable communication apparatus may minimize power consumption.
As set forth above, the portable communication apparatus is required to determine an overhead of the system exactly in order to reduce power consumption. Thus, a technology is required to determine the overhead of the system exactly and to control power consumption according to the determination.